So let's talk about the lyrics Isolde and Kakania were singing at the end of "Through the Glass"!
As the story described, Isolde was singing a part of the opera "Tristan und Isolde," specifically the part where Isolde is waiting for her rendezvous with Tristan.
In this part, Isolde ignores the calling of horns that signals the arrival of King Marke—the king she's supposed to marry—, insisting that it's just the rustling of the wind or the trickling of the stream, even though her maid tells her over and over that it IS the sound of the horns and the king is nearby.
In our Isolde case, I think we can interpret the call of horns as symbolizing the reality that Isolde doesn't hear—or rather, doesn't want to hear. Because "the calling of horns does not sound so sweet" compared to "the silence of the night" (the peaceful dream she doesn't want to wake up from), and the promise of meeting with "He who is waiting for me in the silence of the night," which—I think we can agree—is Kakania in her dream.
And unlike the "run away with me, Cavaradossi" scene, this time Kakania responded with her part!